Studies are continuing on retinal metabolism employing freeze-dried sections of frog retina. The concentrations of adenyl nucleotides (ATP, ADP, and AMP) and P-creatine were measured as a function of dark adaptation or light exposure using 2 sec or 2 min of bright light (approximately 250 ft candles) as well as 2 hrs of dim light (approximately 2.5 ft candles). For AMP, although each area sampled gave discrete tightly-bunched sets of numbers, levels even within one layer could vary up to 2.5 fold. This was not true for the other metabolites measured. A fluorometric assay for calmodulin was developed utilizing its ability to stimulate calmodulin-dependent phosphodiesterase. Sensitivity of the assay ranged from 0.5 to 5 ng. Additional work to further increase the sensitivity is planned. A project will begin to study the adenyl nucleotides, P-creatine, and cyclic nucleotide levels in retinal layers of Irish setter dogs. Levels in normal setters will be compared to levels in dogs with an inherited rod-cone dysplasia in order to gain some insight into the nature and course of this degeneration.